In agriculture, mining, and other industries, there are a wide variety of slurries in need of dewatering. One context is the dewatering of swine, dairy, or beef cattle waste. In confined space, hog, dairy, or beef production, the manure and waste is often collected directly under the barn area. The floors of the barn are slotted, allowing the waste material to accumulate under the barn. This material is diluted by wash water and other liquids and finally is removed by pumping or draining. The waste material is either sent to a lagoon storage area or in many cases used as a fertilizer. The accumulated slurry can be pumped into a tanker truck or wagon and taken to farm fields and applied as liquid manure. Application of this material as a liquid, though, has a number of disadvantages, including environmental damage due to runoff of the liquid into adjacent waterways or ditches. Odor from the liquid manure cause issues with adjacent land owners. Dewatering the waste reduces these liabilities and also reduces the number of trips across the farm fields, reducing soil compaction and lowering fuel costs.
In food processing, slurries are created that contain large amounts of solids which must be removed before the water can be either reused in the process or sent to a waste water treatment facility. Many times these slurries contain solids in need of separation and dewatering, such as potato peelings or grit from the washing processes. In the coal mining process, fine particles of coal are lost in the washing process and must be settled out in large holding ponds. This material can be captured with a proper dewatering process and the coal then reclaimed for sale. In municipal waste water treatment plants, solids are accumulated in digesters. Eventually this slurry must be removed from the digester and dewatered. In the sand and gravel industry the washing process many times produces a slurry stream that contains large amounts of small aggregate material that could be reclaimed by the proper apparatus.
There are many different types of dewatering apparatuses in use today. Many of these are mechanical in nature and require a large amount of energy to operate and specialized skills to maintain. One example is disclosed in Heywood's “Apparatus for Treating Sewage,” U.S. Pat. No. 392,607. Another is disclosed in U.S. Pat. No. 3,970,552, “Method and Means for Separation of Liquids from a Mixture of Solids and Liquids,” to Bongert.
Other examples of mechanical dewatering equipment for accomplishing high volume dewatering of liquid slurries include the following: U.S. Pat. No. 4,116,838, “Sludge Filter,” to Lazzarotto; U.S. Pat. No. 4,929,353, “Portable Liquid-Solid Separator for Bulk Sludge,” to Harris; U.S. Pat. No. 5,156,749, “Dewatering System for Sludge Removal,” to Williams; U.S. Pat. No. 5,589,081, “Divided Phase Separator for Liquid/Solid Separation in Sludge” to Harris; U.S. Pat. No. 5,595,654, “Sludge Filtration System and Method,” to Caughman, Jr.; and U.S. Pat. No. 4,871,454, “Portable Dumpster Slurry Separating System,” to Lott. Such systems may utilize a type of filter, but have mechanical disadvantages and often require tilting of sludge.
Another example is U.S. Pat. No. 4,133,769, “Liquid Filter Having Self-Retaining Filter Bag,” to Morgan, Jr., incorporating a filter bag suspended inside a shell. This device has a major disadvantage in that the dewatered material must be lifted out of the device to dispose or reprocess, limiting the amount of material that can be effectively dewatered due to the weight of the dewatered material. A similar example of is U.S. Pat. No. 5,287,985, “Container for Dewatering or Packaging and Transportation,” to Hatayama. This device has the considerable drawback in that the volume of dewatered material would have to be limited to the weight limitations of the device. Most dewatering processes require large volume and weight capabilities.
Large geotextile bags have been used successfully in dewatering many different types of slurries. Such fabric filter bags are sewn in cylindrical shapes in sizes from six feet in circumference and twelve feet in length to ninety feet in circumference with a length of three hundred 300 feet. Slurry is treated with a flocculent and pumped into the bags, where the solids are captured, and the liquid “bleeds” through the filtration fabric. After the contents have been allowed to dry for various time periods, ranging from a few days to months or even years, the bag is cut open, and the contents are removed. One example of this type of device is found in U.S. Pat. No. 6,186,701, “Elongate Flexible Container,” to Kempers.
A further example of existing technology is found in U.S. Pat. No. 7,112,283, “Method and System for Processing Waste,” to Stephens. This type of slurry dewatering has disadvantages including the handling expense of the consolidated solids and the fact that the required bags must be laid on the ground and subjected to weather-related and drainage issues. In addition, the positioning of the bag on the ground tends to bind the bottom of the bag, which is where the liquid is most likely to drain out. This will cause the liquid to pool inside the bag and increase the drying time required to accomplish the dewatering phase.